Many vehicles today are equipped with a cruise control to make it easier for the driver to drive the vehicle. The desired speed can then be set by the driver, e.g. via a control device in the steering wheel console, and a cruise control system in the vehicle acts thereafter upon a control system so that it accelerates and brakes the vehicle in order to maintain a desired speed. If the vehicle is equipped with an automatic gear change system, the vehicle's gears are changed so that the vehicle can maintain the desired speed.
When a cruise control is used in hilly terrain, the cruise control system will try to maintain a set speed on upgrades. This results inter alia in the vehicle accelerating over the crest of a hill and possibly into a subsequent downgrade, making it necessary to brake to avoid exceeding the set speed, which is a fuel-expensive way of running the vehicle.
By varying the vehicle's speed in hilly terrain it is possible to save fuel as compared with a conventional cruise control. This may be done in various ways, e.g. by calculations of the vehicle's current state (as with Scania Ecocruise®). If an upgrade is calculated, the system then accelerates the vehicle uphill. Towards the end of the climb, the system is programmed to avoid acceleration until the gradient has levelled out at the top, provided that the vehicle's speed does not drop below a certain level. Lowering the speed at the end of an upgrade makes it possible to regain speed on a subsequent downgrade without using the engine to accelerate. When the vehicle approaches the bottom of a dip, the system endeavours to use kinetic energy to embark on the next upgrade at a higher speed than an ordinary cruise control. The system will easily provide acceleration at the end of the downgrade in order to maintain the vehicle's momentum. In undulating terrain, this means that the vehicle starts the next climb at a higher speed than normal. Avoiding unnecessary acceleration and using the vehicle's kinetic energy makes it possible to save fuel.
Cruise controls are not usually adapted to adapting vehicle speed to cater for, for example, speed limits or roundabouts and intersections ahead. This means that even if they try to control the vehicle's speed for the sake of economic running by varying it in hilly terrain and reducing it for comfort and safety at bends, the driver has sometimes him/herself to interrupt, e.g. because the permissible speed is lowered by a traffic sign.
If the topology ahead is made known by the vehicle having map data and GPS, such a system can be made more robust and can also change the vehicle's speed in anticipation.
Published patent application US 2008/0221776 describes a system for changing the settings of the engine's ECM (electronic control module) in order to optimise the engine's characteristics with regard to fuel consumption according to attendant circumstances such as topography, road characteristics and roadworks. The vehicle's geographical position is determined by GPS.
The object of the present invention is to propose an improved cruise control which caters for hindrances ahead and thereby reduces the vehicle's fuel consumption.